Nanoscale roughness of surfaces impacts on surface properties that can in turn influence the performance of a range of devices, which include biomaterials, micro- and nano-electromechanical systems (M/NEMS) and microelectronics. The inherent roughness of lithographically-produced features is commonly termed line edge roughness (LER) or line width roughness (LWR). As the size of lithographically-produced features has reduced, the observed roughness as a percentage of feature size has increased and is now a significant factor to consider when developing manufacturing improvements.
The causes of LER include non-discrete acid diffusion, mask roughness, aerial image contrast and shot noise. Recent studies propose new types of photoresists that can be used to suitably modify LER, including polymer bound PAG resists, non-chemical amplified resists and molecular glass resists. Although efforts have been made to improve photoresist design, the results have to date not been adequate to meet the target levels set by the semiconductor industry. Accordingly, there remains a need for new techniques in which LER can be suitably modified to assist with optimising device performance.